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Old 11th Mar 2019, 09:02
  #277 (permalink)  
Old King Coal
Join Date: Aug 2000
Location: Monrovia / Liberia
Age: 58
Posts: 739
Originally Posted by BRE View Post
So what you are saying is that Boeing have kind of broken their former selling point of allowing the pilot to be in control at all times?
But B737 pilots are not always in control, e.g. the B737 has been doing things automatically (i.e. without pilot input) ever since the introduction of the Speed Trim System (STS).

For those not in the know wrt B737 systems, the speed trim system (STS) is a speed stability augmentation system designed to improve flight characteristics during operations with a low gross weight, aft centre of gravity and high thrust when the autopilot is not engaged. The purpose of the STS is to return the airplane to a trimmed speed by commanding the stabiliser in a direction opposite the speed change. The STS monitors inputs of stabilizer position, thrust lever position, airspeed and vertical speed and then trims the stabiliser using the autopilot stabilizer trim. As the airplane speed increases or decreases from the trimmed speed, the stabilizer is commanded in the direction to return the airplane to the trimmed speed. This increases control column forces to force the airplane to return to the trimmed speed. As the airplane returns to the trimmed speed, the STS commanded stabilizer movement is removed. STS operates most frequently during takeoffs, climb and go-arounds.

So, STS is a bit like MCAS (albeit for slightly different regimes of flight) in that it operates automatically and moves the stabiliser.

Last edited by Old King Coal; 11th Mar 2019 at 09:15.
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